Investigations on the biosynthesis of steroids and terpenoids. Part XII. Biosynthesis of 3β-hydroxy-triterpenoids and -steroids from (3S)-2,3-epoxy-2,3-dihydrosqualene

Barton, D. H. R.; Jarman, T. R.; Watson, K. C.; Widdowson, David A.; Boar, Robin B.; Damps, Kathleen

doi:10.1039/p19750001134

Cited by 49 publications

(19 citation statements)

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“…This property has been shown only for the OSC of M. capsulatus, which harbors an SHC as well as an OSC that is able to accept both enantiomers (78). Other OSCs from animals, yeast, and plants accept only the (S)-enantiomer of 2,3-oxidosqualene as a substrate (6). The less hydrophobic character of their catalytic domains probably is responsible for their inability to initiate the polycyclization of squalene (25).…”

Section: Reaction Mechanismmentioning

confidence: 99%

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Squalene-Hopene Cyclases

Siedenburg

Jendrossek

2011

Appl Environ Microbiol

123

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Hopanoids and sterols are members of a large group of cyclic triterpenoic compounds that have important functions in many prokaryotic and eukaryotic organisms. They are biochemically synthesized from linear precursors (squalene, 2,3-oxidosqualene) in only one enzymatic step that is catalyzed by squalene-hopene cyclase (SHC) or oxidosqualene cyclase (OSC). SHCs and OSCs are related in amino acid sequences and probably are derived from a common ancestor. The SHC reaction requires the formation of five ring structures, 13 covalent bonds, and nine stereo centers and therefore is one of the most complex one-step enzymatic reactions. We summarize the knowledge of the properties of triterpene cyclases and details of the reaction mechanism of Alicyclobacillus acidocaldarius SHC. Properties of other SHCs are included.

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Section: Reaction Mechanismmentioning

confidence: 99%

“…2). The first domain consists of a regular (␣/␣) 6 barrel structure, whereas the second domain shows an ␣-barrel structure in a less periodic manner. Comparisons of the two domains suggest that the second domain may have been developed after gene duplication of the first domain.…”

Section: Structure-function Relationships Of Shcsmentioning

confidence: 99%

Squalene-Hopene Cyclases

Siedenburg

Jendrossek

2011

Appl Environ Microbiol

123

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“…Quantification showed that under the conditions used the cell-free extract from strain 9a converted 36% of racemic 2,3-[3H]oxidosqualene to [3H]-lanosterol. This result corresponds to a 72% conversion of the S-enantiomer of the substrate, for which the enzyme is specific (21). Extracts from pZS2-, pZS4-, and pZSlltransformed SGL9 converted 31, 29, and 29%o of the racemic substrate to product, respectively.…”

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confidence: 99%

Isolation and characterization of the gene encoding 2,3-oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae.

Shi

Buntel

Griffin

1994

Proc. Natl. Acad. Sci. U.S.A.

102

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“…(iv) The two squalene cyclases studied so far, in Acetobacter rancens (29) and Tetrahymena pyriformis (3) are not highly substrate-specific: they cyclize squalene and both enantiomers of its 2,3-epoxide, whereas the squalene epoxide cyclase of eukaryotes acts specifically on the 3(S) enantiomer of the epoxide only, and neither on the 3(R)-epoxide nor on squalene itself (30).$ These criteria single out the hopane family from all other groups of triterpenes; furthermore, most of these are bent molecules, not suitable as reinforcers of a phospholipid matrix despite their amphiphilic character.…”

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confidence: 99%

“…(iii) It implies only a simple polycyclization, without rearrangement or further degradations as in sterol biosynthesis (28)(29)(30).…”

mentioning

confidence: 99%

Molecular evolution of biomembranes: structural equivalents and phylogenetic precursors of sterols.

Rohmer¹,

Bouvier²,

Ourisson³

1979

Proc. Natl. Acad. Sci. U.S.A.

297

176

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Derivatives of one triterpene family, the hopane family, are widely distributed in prokaryotes; they may be localized in membranes, playing there the same role as sterols play in eukaryotes, as a result of their similar size, rigidity, and amphiphilic character. Their biosynthesis embodies many primitive features compared to that of sterols and could have evolved toward the latter once aerobic conditions had been established. Membrane reinforcement appears to be achieved in other prokaryotes by other mechanisms, involving either approximately 40-A-long rigid hydrocarbon chains terminated by one polar group acting like a peg through the double-layer or similar chains terminated by two polar groups acting like tie-bars across the membrane. These inserts can be tetraterpenes (e.g., carotenoids). The biophysical function of membrane optimizers appears to have evolved toward sterols by changes limited to only a few enzymatic steps of the same fundamental biosynthetic processes.

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Investigations on the biosynthesis of steroids and terpenoids. Part XII. Biosynthesis of 3β-hydroxy-triterpenoids and -steroids from (3S)-2,3-epoxy-2,3-dihydrosqualene

Cited by 49 publications

References 0 publications

Squalene-Hopene Cyclases

Squalene-Hopene Cyclases

Isolation and characterization of the gene encoding 2,3-oxidosqualene-lanosterol cyclase from Saccharomyces cerevisiae.

Molecular evolution of biomembranes: structural equivalents and phylogenetic precursors of sterols.

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